The invention is directed to a beam catcher, particularly for a laser beam of a positioning device.
Positioning devices that emit laser beams for marking are used for positioning tasks in the building industry. Particularly, beam catchers that are associated with the positioning devices are used for reliably finding the beam at greater distances and with poorly reflecting substrates and high requirements for positioning accuracy for exact marking and precise determination of a deviation in position.
In conventional passive beam catchers, auxiliary optics such as wedges or Fresnel lenses are used to convert minimal positional differences in the impinging laser light beam into displays which differ qualitatively. In conventional active beam catchers, a photodetector supplied by a power source is used to receive the laser light beam and a display connected to an evaluating circuit is used to determine the offset of the light beam relative to the reference point.
According to U.S. Pat. No. 3,894,230, an active beam catcher for a pulsating laser has a photodetector with a plurality of photodiodes in the form of a pulse-controlled photodiode array which are offset in a defined manner relative to the reference point along a line, an evaluating circuit, and a digital output of the offset of the light beam relative to the reference point. The associated holding circuit, which is capacitance-coupled to each individual photodiode, responds to light pulses of any type so that extraneous or ambient light and stray light can bring about various interference.